This invention relates to a manufacturing method of a semiconductor device, and particularly to a manufacturing method of a semiconductor device such as a power module made by bonding semiconductor device chips to one side of a circuit board and bonding a metal base for dissipating heat produced in the semiconductor device chips to the other side.
In the manufacture of semiconductor devices such as power modules, bonding of multiple heat-sinking, electrically insulating boards to a metal base is carried out by soldering. At this time, in related art, a commercially available solder resist has been printed onto the metal base and dried to prevent solder flow (see, for example, JP-A-6-244224). And, in assembly environments where solder resist cannot be used, solder bonding has been carried out with the boards fixed with a positioning jig or the like.
There is also the method of forming an oxide film on or in depressions in the metal base with a laser beam to prevent solder flow, but when the amount of solder is large (in terms of thickness, 0.05 mm or greater) this is largely ineffective.
However, with the solder resist of related art there has been the problem that cost and time are entailed in making up a screen for printing, and in process steps from printing to drying.
And, with solder resist, because it is generally an organic substance such as epoxy resin, its resistance to solder heat is not exceedingly high. When, for example, fluxless soldering is carried out in a hydrogen gas atmosphere, solderability has been impaired by the production of outgas from the solder resist. There are also problems such as contamination of the device, and thus use has been limited.
The present invention was made in view of such prior art problems. It is an object of the invention to provide a manufacturing method of a semiconductor device in order to make the creation of a dam material for preventing solder flow easy, and furthermore realize high reliability.
Further objects and advantages of the invention will be apparent from the following description of the invention and the associated drawings.